Boilers



April 14, 970 E. A. M. BURNFLELD 3,505,980

BOILERS Filed Aug. 24, 1968 4 Sheets-Sheet 1 INVENTOR Em: Amman "ham. Bukunn! ATTORNEY April 14, 1970 E. A. M. BURNFIELD BOILERS 4 Sheets-Sheet 2 Filed Aug. 24, 1968 IN V E NTOR Emc Magnum Mac"... luuunma BY M M M ATTO R NEY F/GZ April 14, 1970 E. A. M. BURNFIELD BOILERS Filed. Aug. 24, 1968 4 Sheets-Sheet 5 IN V E NTO R in: human mew. Bununem BY M 4% jaw/40L M04 2 ATTORNEY April 14, 1970 E. A. M. BURNFIELD 3,505,980

BOILERS Filed Aug. 24, 1968 f 4 Sheets-Sheet 4 INV ENTOR Em human men Bukuflun f- ATTORNEY I BY United States Patent US. Cl. 122-149 12 Claims ABSTRACT OF THE DISCLOSURE A shell type boiler including a casing surrounding the shell and spaced therefrom, whereof the shell has an end adapted to be closed by a door and air ducting in the door through which air is drawn from the casing passing to the burner.

This invention relates to shell type boilers for producing steam and/or hot water comprising a tubular container or shell constituting the water and steam chamber; a tubular furnace chamber, a tubular furnace flue and a tubular combustion chamber arranged in series within the outer shell with their longitudinal axes extending longitudinally of the outer shell. Such boilers have the outer end of the furnace chamber secured either directly or indirectly to one end of the outer shell, and the wall of the combustion chamber remote from the flue connected either directly or indirectly to the other end of the outer shell, and include a series of smoke tubes extending longitudinally through the interior of the outer shell outside the furnace chamber and flue from the combustion chamber to and through the end wall of the outer shell remote from the combustion chamber.

In such boilers the series of smoke tubes referred to discharge into a chamber (hereinafter referred to as a first chamber) and thence either into an exit flue or chimney at the end of the outer shell remote from the combustion chamber, or the boilers are provided with a second series of smoke tubes (which may or may not be of different diameters from those of the first series) which extend longitudinally through the interior of the outer shell outside the furnace chamber and flue from the first chamber, to a chamber at the end of the outer shell adjacent to the combustion chamber which communicates with an outer flue or chimney.

For convenience such a boiler whether including a first series of smoke tubes only or a first and second series of smoke tubes will be referred to as a shell type boiler.

Conveniently but not necessarily in such boilers the furnace chamber, flue and combustion chamber are coaxially arranged and their axes extending parallel with the longitudinal axis of the outer shell.

A shell type boiler according to the present invention includes a casing surrounding the shell and spaced therefrom and whereof the shell has an end adapted to be closed by a door and air ducting in the door through which air is drawn from the casing before passing to the burner.

The air ducting may be arranged in heat transfer relationship with the end of the shell, and is preferably arranged in heat transfer relationship with a chamber through which the products of combustion pass. When the boiler includes second pass tubes the ducting may be arranged in heat transfer relationship with the chamber through which the products of combustion pass between the first and second pass tubes (hereinafter referred to as the transfer box). The gases issuing from the first pass tubes into the transfer box are at a comparatively high temperature, i.e., in the region of 850 F. to 1000" F. and

air passing through the duct is thus preheated and the door can be kept relatively cool.

The ducting may be of generally annular form in which case the entry and exit may be positioned on opposite sides of the annulus, means being provided for passing air around both sides of the annulus.

In one construction the door has a recessed portion adapted to close against a tube plate and arranged to form the chamber through which the products of combustion pass. The recessed portion may be partitioned to form respectively the chamber for the products of combustion and the air ducting. The recessed position may be provided with heat insulating lagging.

Preferably air is drawn from the end of the casing remote from the door so as to pass along the length of the casing, and the shell is preferably provided with heat insulating lagging around its exterior. Thus by drawing the air over the lagging the air is preheated first, in the casing surrounding the boiler by the heat lost from the boiler shell, secondly by its passage through the part of the door which is in heat transfer relationship with the boiler and-with this arrangement the noise usually associated-with the inlet of air to a fan is effectively suppressed by the passage both through the door and over the lagged surface of the boiler, while the casing and the door are cooled by the passage of the air.

In one convenient construction the air may be drawn into the upper part of the ducting from the casing and passes through the lower part of the ducting into the burner. The air may be impelled by a fan in the door, or in the casing.

The invention may be carried into practice in various ways and two specific embodiments will now be described by way of example with reference to the accompanying drawings, in which:

FIGURE 1 is a diagrammatic view partly in crosssection through a shell type boiler according to the present invention;

FIGURE 2 is an end view of the boiler shown in FIG- URE 1;

FIGURE 3 is a similar view to FIGURE 1 of a modified construction according to the invention; and

FIGURE 4 is a section on the line 22 of FIGURE 3.

As shown in the FIGURES 1 and 2 a boiler shell 1 has arranged therein a furnace tube 2, first pass tubes indicated at 3 through which the products of combustion pass after leaving the furnace tube, and second pass tubes 4 through which the products of combustion pass after leaving the first pass tubes 3. The products of combustion after leaving the second pass tubes 4 are then discharged to atmosphere via a chimney, not shown. The ends of the tubes are secured respectively in front and rear tube plates 5 and 6.

The shell 1 is provided with lagging 7 around its exterior and is encased in an outer casing 8 spaced from the lagging and providing an air space through which air can be drawn from an opening in the rear of the casing, the direction of the air passing through casing being indicated by the-arrows A. A circular door 10 mounted on hinges 11 is adapted to close against the front tube plate 5 and has arranged in it a burner assembly indicated at 12, and extending around it is an annular duct 13 through which combustion air passes from the casing before passing to the burner.

The duct 13 is provided, on the atmospheric side of the door with insulation 14 and on the boiler side of the door with a septum 15 separating it from the gases passing from the first pass tubes 3 to the second pass tubes 4, and constituting the transfer box.

A passage 14A is provided at the upper end of the duct through which air passes into the duct from the casing and the duct is provided with a batfle 15A so as to direct air 3 passing into the duct around both sides of the door. At the lower end of the duct an exit opening is provided through which air passes to the burner, the direction of flow being indicated by the arrows D and E in FIGURE 1.

The air for combustion is thus preheated, first by the passage through the casing and secondly by its passage through the annular duct where it receives heat transferred through the septum by the hot gases flowing between the first and second passes. The passage of the air not only preheats it but also serves to keep the exterior of the door cool and the noise usually associated with the inlet of air to a fan is effectively suppressed by its passage through the door and over the lagged surface of the boiler.

In the modified construction as shown in FIGURES 3 and 4 there is concentrically arranged within the furnace tube 2 a burner tunnel 20 through which combustion air supplied by a fan 22 drawing air from inside the boiler casing, is metered through a damper 23 and then passes into a duct 24. Formed in the end of the shell 1 between the shell and the furnace tube 2 and outside a front tube plate 25 is an annular chamber 26 or transfer box through which the products of combustion pass from the first tubes 3 into the second pass tubes 4. I

Arranged to close the front end of the boiler is a hinged door 27 in which is a duct 28 extending circumferentially around the door adjacent its periphery and situated so as to extend over that part of the door which closes the transfer box. Situated in the upper part of the transfer box is a baffle 30 by which air is directed from the duct 24 to a. port 31 in the door communicating with the duct 28. A further port 32 is provided in the lower part of the door through which the air passes out of the duct 28 and is directed by a bafile 33 in the lower part of the transfer box into a chamber 34 formed between the end of the furnace chamber and the end of the shell, before passing via a series of director plates 35 into the burner tunnel 20.

The air passing into the duct 28 in the door is arranged,

by means of the baffle 30, to pass around both sides of the duct. The air thus passing through the duct28 absorbs heat from the hot gases in the transfer box and also provides for cooling of the door 27 Insulation may be applied to the shell in a similar manner to that shown in FIGURE 1.

In an alternative arrangement the air may enter and leave the duct 28 at adjacent points so that it travels around substantially the whole of the circumferential extent of the door before passing to the burner.

What I claim as my invention and desire to secure by Letters Patent is:

1. A shell type boiler including a burner, a furnace tube, a shell surrounding the furnace tube and defining a region for retaining water, an inlet casing defining the external surface of the shell an inlet passage for combustion air, a door for closing the end of the shell and including ducting for leading air from the inlet passage to the burner when the door is closed, the ducting passing around the edge of the door, conduit means for carrying air to said burner, an inlet in said ducting communicating with said inlet passage when the door is closed, an outlet passage in said ducting communicating with said conduit means, and a baffie for causing the air entering said ducting through said inlet to divide and pass in two parts around opposite sides of the door to said outlet before being led to the burner.

2. A shell type boiler as claimed in claim 1 in which the ducting is arranged in heat transfer relationship with the boiler to permit heating of said combustion air and cooling of said door.

3. A shell type boiler as claimed in claim 2 further comprising a chamber through which the products of combustion from said burner pass, said chamber being in heat transfer relationship with said conducting. e

4. A boiler as claimed in claim 1 in which the ducting is of generally annular form.

5. A boiler as claimed in claim 4 in which said inlet and outlet to the annulus are positioned on opposite sides of the annulus and said baffle provides for passing air around both sides of the annulus.

6. A boiler as claimed in claim 3 in which the door is adapted to close against a tube plate and has a recessed portion arranged to form the chamber through which the products of combustion pass.

7. A boiler as claimed in claim 6 in which the recessed portion is partitioned to form respectively the chamber for the products of combustion, and the air ducting.

8. A boiler as claimed in claim 7 in which the recessed portion is provided with heat insulating lagging.

9. A boiler as claimed in claim 1 in which the inlet passage extends from the end of the casing remote from the door so as to pass :along the length of the casing.

10. A boiler as claimed in claim 1 in which the shell is surrounded by heat insulating lagging. v

11. A boiler as claimed in claim 10 in which said inlet is in the upper part of the ducting and said outlet is at the base of the ducting.

12. A boiler as claimed in claim 1 further comprising a fan in the door for impelling the air.

V References Cited UNITED STATES PATENTS 2,000,733 5/1935 Avery l22l49 2,674,981 4/1954 Clarkson l22l49 XR 2,835,230 5/1958 Cleaver et al l22l49 XR 3,187,726 6/1965 Vander Meulen l22l49 3,265,042 8/1966 Huckabee l22l49 FOREIGN PATENTS 957,229 5/1964 Great Britain.

KENNETH W. SPRAGUE, Primary Examiner US. Cl. X.R. 56 

